MIAMI – President Barack Obama said the "biggest failure" of his presidency is not passing immigration reform, while blaming his failure on Washington which he said cannot be changed "from the inside," the president said in a Spanish-language Univision forum Wednesday.

"My biggest failure so far is we haven't gotten comprehensive immigration reform done," Obama said. "But it's not because for lack of trying or desire, and I'm confident we are going to accomplish that."

The president faced tough questions on why he hadn't accomplished comprehensive immigration reform, an important issue for Hispanic voters. Jorge Ramos, one of the moderators for Univision, put it bluntly: "You promised that and a promise is a promise and with all due respect, you didn't keep that promise."

Obama said on Univision that he accepted responsibility but that he faced an economy "on the verge of collapse" in his first year and blamed Republicans for abandoning support for comprehensive immigration reform.

"What I confess I did not expect, and so I'm happy to take responsibility for being naive here, is that Republicans who had previously supported comprehensive immigration reform, my opponent in 2008 who had been a champion of it and who attended these meetings, suddenly would walk away," he said. "That's what I did not anticipate."

Obama said he only leads the executive branch.

"We have to have cooperation from all these sources to get something done," he said.

Shortly after he spoke, the Republican National Committee sent emails blasting the president for pandering to Latino voters for changing his story to say that his biggest failure was the lack of an immigration reform bill.

The e-mail highlighted four past statements the president made to media outlets, including an interview with CBS in July where he said his biggest mistake was putting policy over storytelling.

"When I think about what we've done well and what we haven't done well," the president said to CBS, "the mistake of my first term - couple of years - was thinking that this job was just about getting the policy right. And that's important. But the nature of this office is also to tell a story to the American people that gives them a sense of unity and purpose and optimism, especially during tough times."

"...All we heard was more excuses on the devastating effects the Obama Administration’s policies have had on the Hispanic community, and yet he offered no plan for the future," the Republicans said in an e-mail to reporters. "He declared that “you can't change Washington from the inside" despite saying that he was running to change it."

In the Univision forum, Obama continued to lay blame on the inability to get Republican cooperation.

"We initiated the meetings...and what we could not get was a single Republican, including the 20 who had previously voted to support comprehensive immigration reform, to step up," he said.

He also said there was "the thinking that the president is somebody who is all-powerful and can get everything done."

Obama also said he was disappointed he hasn't been able to change the tone in Washington from the inside, and he said that American voters have to mobilize and put pressure on Congress for real change.

"The most important lesson I've learned is that you can't change Washington from the inside, you can only change it from the outside," he said. "That's how I got elected, and that's how the big accomplishments like Health Care got done because we were able to mobilize the American people to speak out."

Obama said rival Mitt Romney hasn't "gotten around a lot" if he believes that 47 percent of Americans consider themselves victims and entitled to government help.

Obama explained the country has gone through a challenging time and that people "want a hand up and not a handout."

In suggesting his GOP rival was out of touch, Obama was reacting to secretly taped remarks by Romney in which the Republican declared that the 47 percent of voters who support Obama represent Americans who don't pay income taxes and "who believe that government has a responsibility to care for them."

Obama said Americans pay payroll taxes, gas taxes and state and sales taxes. He noted that those who don't pay income taxes include workers who don't make enough money to qualify, older Americans and students.

"When you express an attitude that half the country considers itself victims, that somehow they want to be dependent on government, my thinking is maybe you haven't gotten around a lot," Obama said.